Java - How to calculate the first and last day of each week

Question

I'm trying to create a weekly calendar that looks like this: http://dhtmlx.com/docs/products/dhtmlxScheduler/sample_basic.html

How can I calculate every week date? For example, this week is:

Monday - Sunday
7 June, 8 June, 9 June, 10 June, 11 June, 12 June, 13 June

I don't understand where is the problem. Try to reword the question. — Xorty, Jun 11 '10 at 13:55

score 45 · Accepted Answer · answered Jun 11 '10 at 14:01

45

I guess this does what you want:

// Get calendar set to current date and time
Calendar c = Calendar.getInstance();

// Set the calendar to monday of the current week
c.set(Calendar.DAY_OF_WEEK, Calendar.MONDAY);

// Print dates of the current week starting on Monday
DateFormat df = new SimpleDateFormat("EEE dd/MM/yyyy");
for (int i = 0; i < 7; i++) {
    System.out.println(df.format(c.getTime()));
    c.add(Calendar.DATE, 1);
}

answered Jun 11 '10 at 14:01

Jesper

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Thank you this is what I want, if i want previous button can get last week date any idea? – user236501 Jun 11 '10 at 14:07
Class `Calendar` contains methods for date arithmetic. To move it back a week (7 days), do `c.add(Calendar.DATE, -7);`, for example. – Jesper Jun 11 '10 at 14:10
Thank You very much appreaciate your help . – user236501 Jun 11 '10 at 14:11
15

Instead of hardcoding Calendar.MONDAY as the first day of the week, you should use `Calendar#getFirstDayOfWeek()` instead, since the scope of a week is locale dependent. – jarnbjo Jun 11 '10 at 14:53
2

However, your code simply _does not work reliably_. See my comment below and http://stackoverflow.com/questions/6722542 for an explanation. – Michael Piefel Sep 28 '11 at 14:15
jarnbjo, I love you! You solved my bug! I wanna buy you a beer. – 0xRLA Oct 02 '16 at 08:22
FYI, the troublesome old date-time classes such as `java.util.Date`, [`java.util.Calendar`](https://docs.oracle.com/javase/9/docs/api/java/util/Calendar.html), and `java.text.SimpleDateFormat` are now [legacy](https://en.wikipedia.org/wiki/Legacy_system), supplanted by the [java.time](https://docs.oracle.com/javase/9/docs/api/java/time/package-summary.html) classes built into Java 8 & Java 9. See [Tutorial by Oracle](https://docs.oracle.com/javase/tutorial/datetime/TOC.html). See [Answer by Przemek](https://stackoverflow.com/a/33868624/642706). – Basil Bourque Dec 29 '17 at 07:34

Gregor Koukkoullis · Answer 2 · 2016-03-09T10:04:52.247

With the new date and time API in Java 8 you would do:

LocalDate now = LocalDate.now();

// determine country (Locale) specific first day of current week
DayOfWeek firstDayOfWeek = WeekFields.of(Locale.getDefault()).getFirstDayOfWeek();
LocalDate startOfCurrentWeek = now.with(TemporalAdjusters.previousOrSame(firstDayOfWeek));

// determine last day of current week
DayOfWeek lastDayOfWeek = firstDayOfWeek.plus(6); // or minus(1)
LocalDate endOfWeek = now.with(TemporalAdjusters.nextOrSame(lastDayOfWeek));

// Print the dates of the current week
LocalDate printDate = startOfCurrentWeek;
DateTimeFormatter formatter = DateTimeFormatter.ofPattern("EEE dd/MM/yyyy");
for (int i=0; i < 7; i++) {
    System.out.println(printDate.format(formatter));
    printDate = printDate.plusDays(1);
}

Przemek · Answer 3 · 2015-12-23T15:04:15.953

Java.time

Using java.time library built into Java 8:

import java.time.DayOfWeek;
import java.time.LocalDate;
import static java.time.temporal.TemporalAdjusters.previousOrSame;
import static java.time.temporal.TemporalAdjusters.nextOrSame;

LocalDate now = LocalDate.now(); # 2015-11-23
LocalDate first = now.with(previousOrSame(DayOfWeek.MONDAY)); # 2015-11-23
LocalDate last = now.with(nextOrSame(DayOfWeek.SUNDAY)); # 2015-11-29

You can iterate over DayOfWeek.values() to get all current week days

DayOfWeek.values(); # Array(MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY, SUNDAY)
for (DayOfWeek day: DayOfWeek.values()) {
    System.out.print(first.with(nextOrSame(day)));
} # 2015-11-23, 2015-11-24, 2015-11-25, 2015-11-26, 2015-11-27, 2015-11-28, 2015-11-29

score 9 · Answer 4 · answered Jun 11 '10 at 13:57

9

First day of this week.

    Calendar c = Calendar.getInstance();
    while (c.get(Calendar.DAY_OF_WEEK) != Calendar.MONDAY) {
        c.add(Calendar.DATE, -1);
    }

answered Jun 11 '10 at 13:57

Nikita Rybak

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1

It's not necessary to step back to Monday day by day, you can just `c.set(Calendar.DAY_OF_WEEK, Calendar.MONDAY);` to set the calendar to Monday of the current week (see my answer). – Jesper Jun 11 '10 at 14:02
5

Absolutely not, @Jesper. Setting the day of the week does not necessarily move backwards. – Michael Piefel Dec 15 '11 at 20:59
Simple and elegant solution! – Exterminator13 Feb 21 '16 at 22:37

score 6 · Answer 5 · answered Sep 21 '11 at 11:51

Simply setting the day of week does not seem to be reliable. Consider the following simple code:

Calendar calendar = Calendar.getInstance(Locale.GERMANY);
calendar.set(2011, Calendar.SEPTEMBER, 18);
System.out.printf("Starting day: %tF%n", calendar);

calendar.set(Calendar.DAY_OF_WEEK, Calendar.MONDAY);
System.out.printf("Last monday: %tF%n", calendar);
System.out.printf("First day of week: %d%n", calendar.getFirstDayOfWeek());

The result of running this program is:

Starting day: 2011-09-18
Last monday: 2011-09-19
First day of week: 2

In other words, it stepped forward in time. For a German locale, this is really not the expected answer. Note that the calendar correctly uses Monday as first day of the week (only for computing the week of the year, perhaps).

score 2 · Answer 6 · answered Jun 11 '10 at 14:07

You can build up on this: The following code prints the first and last dates of each week for 15 weeks from now.

Calendar c = Calendar.getInstance();
c.set(Calendar.DAY_OF_WEEK, Calendar.MONDAY);
for(int i=0; i<15; i++)
{
    System.out.print("Start Date : " + c.getTime() + ", ");
    c.add(Calendar.DAY_OF_WEEK, 6);
    System.out.println("End Date : " + c.getTime());
    c.add(Calendar.DAY_OF_WEEK, 1);
}

score 1 · Answer 7 · answered Jun 11 '10 at 13:55

1

If you know which day it is (Friday) and the current date (June 11), you can calculate the other days in this week.

answered Jun 11 '10 at 13:55

Sjoerd

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score 1 · Answer 8 · answered Jun 11 '10 at 13:57

1

I recommend that you use Joda Time library. Gregorian Calendar class has weekOfWeekyear and dayOfWeek methods.

answered Jun 11 '10 at 13:57

kgiannakakis

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score 1 · Answer 9 · answered Apr 26 '16 at 04:21

    Calendar startCal = Calendar.getInstance();
    startCal.setTimeInMillis(startDate);
    Calendar endCal = Calendar.getInstance();
    endCal.setTimeInMillis(endDate);
    SimpleDateFormat sdf = new SimpleDateFormat("dd-MMMM-yyyy");
    while (startCal.before(endCal)) {
        int weekNumber = startCal.get(Calendar.WEEK_OF_YEAR);
        Calendar cal = Calendar.getInstance();
        cal.set(Calendar.DAY_OF_WEEK, Calendar.SUNDAY);
        cal.set(Calendar.WEEK_OF_YEAR, weekNumber);
        Date sunday = cal.getTime();
        Log.d("sunday", "" + sdf.format(sunday));
        cal.set(Calendar.DAY_OF_WEEK, Calendar.SATURDAY);
        cal.set(Calendar.WEEK_OF_YEAR, weekNumber);
        Date saturday = cal.getTime();
        Log.d("saturday", "" + sdf.format(saturday));
        weekNumber = weekNumber + 1;
        startCal.set(Calendar.WEEK_OF_YEAR, weekNumber);

    }

score 0 · Answer 10 · answered Jun 11 '10 at 14:00

0

The algorithm you're looking for (calculating the day of the week for any given date) is "Zeller's Congruence". Here's a Java implementation:

http://technojeeves.com/joomla/index.php/free/57-zellers-congruence

answered Jun 11 '10 at 14:00

Ant

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theres another implementation @ http://helpdesk.objects.com.au/java/zellers-congruence-in-java". Though as mentioned in that post your better off using the Calendar class - http://helpdesk.objects.com.au/java/use-calendar-class-to-get-localized-day-names, which can also be used to get the first day of the week - http://helpdesk.objects.com.au/java/how-do-i-get-the-date-of-first-day-of-the-current-week – objects Nov 21 '10 at 01:30

score -1 · Answer 11 · answered Jun 11 '10 at 13:54

-1

Yes. Use Joda Time

http://joda-time.sourceforge.net/

answered Jun 11 '10 at 13:54

user334583

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Java - How to calculate the first and last day of each week

11 Answers11

Java.time

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